Hydraulic brake equalizer



May 31, 1938. F. J. BACHMANN l 2,119,001

HYDRAULIC BRAKE EQUALIZER Filed Sepp 4, 1936 il zu ,ep ,ik l l 1424. .7

Patented vMay 31, 1938 UNITED STATES PATENT oFFlcE This invention relates to brake mechanism for motor vehicles and the like and more especially to means for actuating and equalizing` hydraulic brakes. Hydraulic brakes for motor vehicles as constructed heretofore possess an important in. herent weakness. A complete failure of the brakes often results because of a leak in one of the pipe lines between the actuating means or master cylinder and its associated operating mechanism on the wheel. It is to overcome this dangerous and objectionable condition that my present invention has been developed, as will be clear from the following specification.

It is therefore a general object of the invention to provide a simple, practical, and reliable brake actuating mechanism of the character described.

Another object is to provide insuch a brake mechanism means for automatically isolating any particular brake wheel actuating mechanism that has become inoperative because of a leak in the system leading to that brake, and at the same time maintaining complete operativeness and balance of the remaining wheel brakes.

Other related objects and advantages will appear and be brought out more fully in the following description, reference being had to the accompanying drawing, wherein:

Fig. Ii is an elevation in central section of apreferred embodiment of my invention;

Fig. 2 is a cross-sectional elevation taken along the line 2-2 of Fig. 1;

Fig. 3 is a similar view taken along the line 3--3 of Fig. 1;

Fig. 4 is 'a fragmentary sectional view taken along the line 4 4 of Fig. 1; and

Fig. 5 is a fragmentary view illustrating one of the valves comprising an important feature of the invention.

Referring more particularly to the drawing, I show hydraulic brake equalizing and actuating mechanism generally by the numeral I0, which consists essentially of a metallic housing II preferably of cast iron or equivalent material, in the upper portion of which is a reservoir I2 for the operating fluid which is usually aV specially prepared oil. In the lower portion of the housing I have provided a main cylinder I3 open at one end in which is adapted to reciprocate a master piston I4, the clearance between the piston and the cylinder being very small in order to prevent the leakage of the liquid past the walls of the piston. It may be found advisable under certain circumstances in order to prevent leakage of the liquid past the piston I4 and the pistons 32 as herein'- after described to provide a packing ring.l However, as this is considered a matter to be determined as met in practice, the details of which are "well understood by automotive engineers, I have notvattempted to show any particular form of such a seati but it will be understood that such a seal may be employed if found desirable or necessary.

The piston I4 is actuated or reciprocated by an adjustable push rod I5 connected to the usual motor vehicle brake pedal, the details of which arrangement are well known to those sln'lled in the art and not shown further herein. A bracket I6 supports the housing II, being suitably secured 'thereto by bolts or otherwise, and is secured to a convenient portion of the frame of the motor vehicle by mounting bolts I'I. A suitable cover I8 is provided for the reservoir I2 to which it is secured by bolts I9 threaded into bosses 20 in the upper part of the housing Il. The cover I8 has a shouldered filling aperture 2| closed by a threaded square head plug 22 suitably provided with Ventilating passages 23. An inlet port 24 leads from the reservoir I2 to cylinder I3 whereby the cylinder is normally kept full of liquid from the reservoir I2, the normal or inoperative position of the piston I4 being in the position shown in Fig. 1. A pair of cylinders 25 are located in the upper portion of the housing II and in a manner similar to cylinder I3 have an open end. A

similar pair of open end cylinders 26 are located in the lower portion of the housing I I, the cylinders 25 and 26 each having a communicating passageway or port 2l connecting them with the master or main cylinder I3.

Elbow couplings 28 connect the upper cylinders 25 with pipes 29 which lead to two of the motor vehicle wheel brakes and preferably to the front wheel brakes for a reason which will be apparent hereinafter. Similarly elbow couplings 30 connect cylinders 2 with pipes 3| leading to the remaining two wheels of the vehicle. In each of the cylinders 25 and 26 is located an equalizing piston or valve 32, the pistons being adapted to reciprocate in the cylinders in a manner similar to piston I4. The cylinders 25 and 26 together with ports 21 provide passageways between the master cylinder I3 andthe pipes 29 and 3I, and

together withpistons 32 comprise shut-off valve end of a spring 34. A resilientsnap ring 35 is retained by its resiliency in a semi-circular groove Y'36 adjacent the openend of cylinder I3 and serves as a stop for the piston I4, as will be clear from Fig. 1. The piston I4 has a reduced portion 31 and a further reduced end portion 35, the latter being secured to a circular ilange member 35 having a bore 45 adapted to receive the reduced portion 35. The member 35 has a flange ring 4| having a face 4Ia adapted for a function to 'be described hereinbelow. A hub 42 is also provided on member 35 and a locking pin 45 secures the piston-member .|4 to flange member 35. In the opposite end of member 35 a conical bore 44 is formed in an extension 45 of the member 55, bore 44 having a rounded seat 45 adapted for engagement with the rounded end 41 of a push rod extension member 45. The member 45 has a threaded borel 45 and a flange 55, the bore 45 having a threaded attachment to a threaded portion 5I of push rod I5, a suitable locking nut 52 being provided to prevent loosening of these parts. 'Ihe rod I5 has a pivoted end 55 for engagement withthe operating arm of the brake pedal.

A neck 54 is formed on the housing II and has a groove and a flange 55 adapted for the attachment of one end of a tubular flexible boot 51, the terminal edge of the boot having a bead 55 adapted to be retained in the groove 55, and a locking ring 59 may be employed to secure the bead 55 in groove 55. A similar beaded neck 55 is formed at the opposite end of the boot 51, a

similar locking ring 5I being provided to securel the neck 55 to the flange 55.

The pistons 32, one of which is shown in detail in Fig. 5, each have a reduced portion 52 and a shoulder 53, the latter being adapted to secure the piston against removal from the cylinder 25 with a snap ring 54 located in a semi-circular groove 55 in the cylinder wall. A coil spring 55 is retained in position around the reduced portion 52 of each piston 32, one end of the spring 55 being against the .shoulder 53, the spring having a free end 51 which in normal position is spaced a short distance from the face 4Ia of the ring 4|. The reduced portion 52 of each piston 32 has an end face 53. Each piston 32 is preferably provided with a circular groove 59 in which a locking screw 10 is adapted to be advanced when under certain circumstances it is desired to lock the pistons 32. Each screw 15 is secured in a threaded bore 1I in the housing |I, lock nuts 12 being employed to hold the screws 15 in retracted position as shown in Fig. 4 during normal actuation of the brake mechanism. The pistons 32 are locked by the screws 15 when it is desired to flll the pipe lines 29 and 3| initially, after a necessary bleeding of the pipes during servicing, or after damage to any of the pipes or brake mechanism, as will be apparent hereinafter. A threaded bore 13 may be provided in the end wall of the cylinder I3 for the reception of the well-known stop light switch 14.

The operation of my invention is as follows: Assuming the pipes 23 and 3|, the cylinders I3, 25, and 25, and reservoir I2 to be filled with the proper actuating oil or other fluid, the brake pedal upon being depressed will actuate push rod I5 to the right as shown in Fig. 1, forcing the master piston I4 to the right a short movement which will carry its free end beyond inlet port 24, further movement of which will develop a pressure in cylinders I3, 25, and 25, and pipes 29 and 3|, thus actuating the brakes on the wheels of a motor vehicle, the liquid from cylinder I3 passing to cylinders 25 and 25 through passageways or ports 21. 'I'he initial movement of the pedal and push rod I 5 will create this pressure in the cylinders 25 and 25 which pressure will operate to maintain the pistons 32 in the left end oi' cylinders 25 and 25 or against the stop rings 54. Subsequent forward movement of the pedal and push rod I5 will cause face 4Ia of the flange ring 4I to press against free ends 51 of the springs 55, the other ends of which will press against the shoulders 33 of pistons 32. This movement would have a tendency to move the pistons 32 to the right, which movement, however, is prevented inasmuch as the spring tension of the springs 55 is insufficient to overcome the fluid pressure against the opposite ends of the pistons 32.

If, however, any one of the pipes 29 or 3| has developed a leak permitting the removal of the fluid therein, there will not be suilicient pressure developed in its associated cylinder 25 or 25 to retain piston 32 in its initial position, and the movement of rod I5 and flange ring 4I upon reaching the end 51 of the spring 55 will now cause the piston 32 associated with the faulty pipe to be shifted to the right, a small movement of which will carry the end past its associated port 21. thus shutting off the pipe and permitting the pressure of the master cylinder to be maintained inthe remaining pipe lines,.it being understood that this pressure will be equalized in these pipes by ports 21, and the actuation of the brakes associated therewith will occur. The piston or pistons 32 which have thus been shifted to the right upon the failure of such faulty pipe lines 29 or 3| will thereafter be maintained in position to keep their respective ports 21 closed during subsequent operation of the brakes and until the faulty line has been repaired, there being no way in which said pistons can be returned to the normal position except the actual return thereof by a service man by a proper tool such as a pair of pliers applied to the reduced portion 52 or by the removal of one of the fittings 25 or 30 and a rod or screwdriver used at the right end.

In the event that the fluid should have escaped from the master cylinder I3 but suillcient fluid was retained in one or more of the small cylinders, for instance the lower cylinders 25, the brakes associated with the cylinders 25 can be operated by suillciently great movement of the push rod I5, initial movement of which would close off ports 21 and engagement would occur' between the ends 53 of the associated pistons 32 and the face 4Ia of flange ring 4I. This would enable the pedal pressure to positively move the said pistons 32 to create sutllcient presure in the cylinders 25 to actuate the brakes connected with the pipes 3| and thus sufdcient brake mechanism would be employed on the motor vehicle to prevent an accident. It will be understood that such braking action would ordinarily be indicated to the driver in time for necessary repairs to be made.

For the reasons 'just pronounced the brake cylinders 25 and 25 have been preferably arranged around the master cylinder I3. However, commercial practice may show that it is satisfactory to have them all arranged below the master cylinder i3, it being understood that the embodiment shown is illustrative of my invention and 'not intended to limit its mode of application.

While I have illustrated and described the preferred form of construction for carrying my inventioninto effect, this is capable of variation and modification without departing from the spirit of the invention. I, therefore, do not wish to be limited to the precise details of construction set forth, but desire to avail myself of such variations and modifications-as come within the scope o1' the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Hydraulic brake actuating and equalizing means as described, comprising a liquid reservoir, a pressure cylinder, a piston in said cylinder adapted to create said pressure pedal actuated means engaging said piston, a plurality of pipes each connecting said cylinder and one oi the brakes; said pipes adapted to retain liquid therein, whereby to transmit said pressure to said brakes, and means adapted upon the failure of any one of said pipes to transmit said pressure to close o said pipe from said cylinder, said means including a valve adapted to be kept inoperative by normal pressure in said pipe and.

adapted to be operated upon subnormal pressure occurring in said pipe said valve adapted to be engaged by and actuated by said' pedal actuated means.

2. Hydraulic brake actuating and equalizing means as described, comprising a housing, a cylinder, a pluralityof pipes each connecting said cylinder to one of the brakes, a reservoir adapted to keep said cylinder and pipes illled with actuating fluid, a pedal actuated piston adapted to create pressure in said cylinder and pipes, a passageway in said housing for each of said pipes to said cylinder, and a pedal actuated valve in each of said passageways adapted to close its respective passageway upon the inability or its associated pipe to maintain said pressure.

3. Hydraulic brake actuating and equalizing means as described, comprising a housing, a cylinder, a plurality of pipes each connecting said cylinder to one of the brakes, a reservoir adapted to keep said cylinder and pipes nlled with actuating iluid, a pedal actuated piston adapted to create pressure in said cylinder and pipes, a passageway in said housing for each of said pipes to said cylinder, and a pedal actuated valve in each of said passageways adapted to close its respective passageway upon the inability of its associated pipe to maintain said pressure, said valves adapted to be normally retained in inoperative position by said pressure.

4. Hydraulic brake actuating and equalizing means as described, comprising a housing having a liquid reservoir and a pressure cylinder. a piston in said cylinder adapted to create said pressure, pedal engaging and actuating means for said piston, a plurality of valve cylinders in said housing, a passageway between each said valve cylinder and said pressure cylinder, a plunger valve in each said valve cylinder adapted when actuated to close oiI its said passageway to said pressure cylinder, each said valve having a stem adapted to engage said pedal actuating means, and a pipeconnecting each said valve cylinder and one of the brakes, said valves each being adapted to be normally held open by said pressure, and to be actuated by said pedal actuating means to close of! its said passageway upon the inability of its associated pipe to maintain said pressure.

5. Hydraulic brake actuating and equalizing means as described, comprising a housing having a liquid reservoir and a pressure cylinder, a piston in said cylinder adapted to create said pressure, pedal engaging and actuating means for said piston, a plurality of valve cylinders in said housing, a passageway between each said valve cylinder and said pressure cylinder, a plunger valve in each said valve cylinder adapted when actuated to close ofi its said passageway to said pressure cylinder, each said valve having a stem and a spring adapted to engage said pedal actuating means, and a pipe connecting each said valve cylinder and one 'of the brakes, said valves each being adapted to be normally held open by said pressure, and to be actuated by said pedal actuating means and spring to close off its said passageway upon the inability of its associated pipe to maintain said pressure.

6. Hydraulic brake actuating and equalizing means as described, comprising a housing having a liquid reservoir and a pressure cylinder, a piston in said cylinder adapted to create said pressure, pedal engaging and actuating means for said piston, a plurality of valve cylinders in said housing, a passageway between each said valve cylinder and said pressure cylinder. a plunger valve in each said valve cylinder adapted when actuated to close oil its said passageway to said pressure cylinder, each said valve having a stem adapted to engage said pedal actuating means, and a pipe connecting each said valve cylinder and one of the brakes, said valves each being adapted to be normally held open by said pressure, and to be actuated by said pedal actuating means to close oi! its said passageway to said pressure cylinder upon the inability of said pressure cylinder to maintain its said pressure.

'7. Hydraulic brake actuating and equalizing means as described, comprising a housing having a liquid reservoir and a pressure cylinder, a piston in said cylinder adapted to create said pressure, pedal engaging and actuating means for said piston, a plurality "of valve cylinders in valve cylinder and said pressure cylinder, a plunger valve in each said valve cylinder adapted when actuated to close on its said passageway to said pressure cylinder, each said valve having a stem and a spring adapted to engage said pedal actuating means, and apipe connecting each said valve cylinder and one of the brakes, said valves each being adapted to be normally held open by said pressure, and to be actuated by said pedal actuating means and spring to close off its said passageway to said pressure cylinder upon the inability o! said pressure cylinder to maintain its said pressure.

FRANK J. BACH'MANN.

said housing, a passageway between each said, 

